Update dgraph/cmd/migrate README.md. (#5495)

This commit is meant to update the instructions for using `dgraph/cmd/migrate` to work with Dgraph 20.03.x.

dgraph/cmd/migrate/README.md

@@ -1,21 +1,29 @@
-install the Dgraph binary from source
+Install the latest Dgraph binary from source
 ```
-go get -v github.com/dgraph-io/dgraph/dgraph
+curl https://get.dgraph.io -sSf | bash
 ```
 
-create a config.properties file that has the following options
+
+Create a config.properties file that has the following options (values should not be in quotes):
 ```
 user = <the user for logging in to the SQL database>
 password = <the password for logging in to the SQL database>
 db = <the SQL database to be migrated>
 ```
 
-export the SQL database into a schema and RDF file, e.g. the schema.txt and sql.rdf file below
+
+Export the SQL database into a schema and RDF file, e.g. the schema.txt and sql.rdf file below
 ```
 dgraph migrate --config config.properties --output_schema schema.txt --output_data sql.rdf
 ```
 
-import the data into Dgraph with the live loader (the example below is connecting to the Dgraph zero and alpha servers running on the default ports)
+If you are connecting to a remote DB (something hosted on AWS, GCP, etc...), you need to pass the following flags
+```
+-- host <the host of your remote DB>
+-- port <if anything other than 3306>
+
+
+Import the data into Dgraph with the live loader (the example below is connecting to the Dgraph zero and alpha servers running on the default ports)
 ```
 dgraph live -z localhost:5080 -a localhost:9080 --files sql.rdf --format=rdf --schema schema.txt
 ```